Electrical conduction behaviour of high energy ion irradiated Kapton-H polyimide film

Abstract

High energy ion irradiation effects on the conduction behaviour of Kapton-H polyimide have been investigated. Kapton-H samples of 125 μm thickness were irradiated with 100 MeV Si + beam for fluences 2.3×10 11, 4.3×10 11 and 1.15×10 12 ions/cm 2 at Nuclear Science Center (PELLETRON FACILITY), New Delhi. Measurements under both transient and the steady state conditions at different temperatures were made at different electric fields ranging from 24 to 160 kV/cm. The transient current behaviour is hyperbolic in nature up to 423 K. Above 423 K the currents are transient free. The decay rate decreases with increasing fluence. The transient currents have mainly been attributed to the formation of free radicals in irradiated Kapton-H polyimide. Non-linear nature of field-current plots is temperature and fluence dependent and an attempt has been made to explain these curves taking into account the various conduction processes. The ionic jump distance estimations do not support ionic hopping as a conduction process. The Poole-Frenkel and Schottky coefficient estimations show that both Poole-Frenkel and Schottky conduction mechanisms are the possible mechanisms operative at high and intermediate temperatures, respectively. The activation energies were determined to be 0.2 and 1.5 eV in the temperature regions below and above 393 K indicating the presence of more than one type of trapping centres in irradiated Kapton-H.